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United States Patent |
6,153,013
|
Sakai
,   et al.
|
November 28, 2000
|
Deposited-film-forming apparatus
Abstract
The deposited-film-forming apparatus of the present invention is an
apparatus for forming deposited films while continuously passing a
belt-like member through the insides of a plurality of vacuum chambers
connected via connecting members and superposingly forming a plurality of
different thin films on the surface of the belt-like member by
plasma-assisted CVD, wherein the vacuum chambers are fixed to a stand for
supporting the vacuum chambers, and a mechanism for relaxing stress acting
in the transport direction of the belt-like member, generated in the
vacuum chambers by the action of expansion and contraction due to thermal
expansion of the vacuum chambers, is provided between each vacuum chamber
and each connecting member.
Inventors:
|
Sakai; Akira (Kyoto, JP);
Okabe; Shotaro (Nara, JP);
Kanai; Masahiro (Kyoto, JP);
Kohda; Yuzo (Kyoto, JP);
Hori; Tadashi (Nara, JP);
Nishimoto; Tomonori (Kyoto, JP);
Yajima; Takahiro (Kyoto, JP)
|
Assignee:
|
Canon Kabushiki Kaisha (Tokyo, JP)
|
Appl. No.:
|
800512 |
Filed:
|
February 14, 1997 |
Foreign Application Priority Data
| Feb 16, 1996[JP] | 8-054170 |
| Feb 16, 1996[JP] | 8-054175 |
Current U.S. Class: |
118/719; 118/723R; 118/729; 118/730; 204/298.25; 257/E31.042 |
Intern'l Class: |
C23C 016/06 |
Field of Search: |
118/719,729,730,723
156/345 PC,345 MC
204/298.25,298.35
|
References Cited
U.S. Patent Documents
4400409 | Aug., 1983 | Izu et al. | 427/39.
|
4438723 | Mar., 1984 | Cannella et al. | 118/718.
|
4951602 | Aug., 1990 | Kanai | 118/719.
|
5102279 | Apr., 1992 | Ezaki et al. | 414/217.
|
Foreign Patent Documents |
61-288074 | Dec., 1986 | JP.
| |
6-1288074 | Dec., 1986 | JP.
| |
Other References
Henkel, D.P.; Doolittle, L.R.; J. Vac. Sci. Technol. A 12(5), Sep./Oct.
1994.
Henkel, et al, J. Vac. Sci. Technol. A 12(5), Sep. 1/Oct. 1994.
Ishimaru, H., J. Vac. Sci. Technol. A 2 (2), Apr. 1-Jun. 1984.
Momose, T., J. Vac. Sci. Technol. A 9 (4), Jul. 1/Aug. 1991.
Ishimaru, et al, J. Vac. Sci. Technol. A 6 (3), May 1/Jun. 1988.
Gutleben, H., et al J. Vac. Sci. Technol. A 9 (1), Jan. 1/Feb. 1991.
Fitch, J.T., et al, J. Vac. Sci. Technol. A 11 (15), Sep. 1/Oct. 1993.
|
Primary Examiner: Mills; Gregory
Assistant Examiner: Zervigon; Rudy
Attorney, Agent or Firm: Fitzpatrick, Cella, Harper & Scinto
Claims
What is claimed is:
1. A deposited-film-forming apparatus comprising a plurality of vacuum
chambers connected to one another, a member transportable through said
plurality of vacuum chambers and capable of receiving desired treatments
therein, and a mechanism for relaxing stress generated in a direction of
movement of said member in said vacuum chambers by expansion and
contraction thereof due to heat, wherein said mechanism for relaxing
stress is a sliding mechanism for allowing said vacuum chambers to slide
over a surface, provided between said vacuum chambers and said surface
atop a stand for supporting said vacuum chambers.
2. The deposited-film-forming apparatus according to claim 1, wherein said
sliding mechanism comprises a warped member attached to each leg of said
vacuum chambers in contact with said surface.
3. The deposited-film-forming apparatus according to claim 1, wherein said
sliding mechanism comprises a spherical member attached to each leg of
said vacuum chambers in contact with said surface.
4. The deposited-film-forming apparatus according to claim 1, wherein said
sliding mechanism comprises a wheel-like member attached to each leg of
said vacuum chambers in contact with said surface.
5. The deposited-film-forming apparatus according to claim 1, wherein said
sliding mechanism is constituted so as to limit a shift thereof in a
direction right-angled to the transport direction of the belt-like member
which passes through said vacuum chambers.
6. The deposited-film-forming apparatus according to claim 1, wherein a
lubricant is provided between said sliding mechanism and said surface of
said stand.
7. The deposited-film-forming apparatus according to claim 1, wherein at
least a part of said vacuum chambers is fixed to said stand.
8. The deposited-film-forming apparatus according to claim 1, wherein said
vacuum chambers each has means for forming a deposited film by chemical
vapor deposition, sputtering or vacuum deposition.
9. The deposited-film-forming apparatus according to claim 8, wherein a
belt-like member passes through said vacuum chambers each having said
means for forming a deposited film by chemical vapor deposition, the
belt-like member has a cylindrical bending portion, and plasma is
generated at said cylindrical bending portion.
10. The deposited-film-forming apparatus according to claim 1, further
comprising gas gates provided between said vacuum chambers.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a deposited-film-forming apparatus for
superposingly forming a plurality of different thin films on the surface
of a belt-like member by plasma-assisted chemical vapor deposition (CVD).
More specifically, it relates to an apparatus for continuously
mass-producing photovoltaic devices such as solar cells by using a
roll-to-roll system.
2. Related Background Art
With regard to photovoltaic devices, semiconductor layers which are
important constituents thereof have semiconductor junctions such as pn
junctions or pin junctions.
When thin-film semiconductors such as amorphous silicon (hereinafter, often
a-Si) are used, material gases containing elements such as phosphine
(PH.sub.3) and diborane (B.sub.2 H.sub.6) acting as dupants are mixed with
a main material gas such as silane, and glow-discharge decomposition is
effected to obtain semiconductor layers having desired conductivity types.
It is known that these semiconductor layers are successively superposingly
formed on a desired substrate, thus the above semiconductor junctions can
be achieved with ease. Accordingly, to produce photovoltaic devices of an
a-Si type, methods are proposed in which independent film-forming chambers
for forming the respective semiconductor layers are successively provided
and each semiconductor layer is formed in each film-forming chamber. In
this connection, U.S. Pat. No. 4,400,409 discloses a continuous
plasma-assisted CVD apparatus employing a roll-to-roll system.
As reported therein, according to this apparatus, a plurality of
glow-discharge regions are provided and a sufficiently long, flexible
substrate having a desired width is provided along the course where the
substrate passes successively through the glow discharge regions. The
substrate is continuously transported in its longitudinal direction while
semiconductor layers with required conductivity types are deposited in the
respective glow-discharge regions, whereby devices having semiconductor
junctions can be continuously produced.
The above apparatus also utilizes gas gates which are used so that dopant
gases used when the semiconductor layers are formed can be prevented from
diffusing and mixing into other glow-discharge regions.
Stated specifically, the respective glow-discharge regions are separated
from each other by slit-shaped separation paths, and means for flowing
scavenging gas such as Ar or H.sub.2 through the separation paths are
employed.
However, in such a conventional vacuum apparatus, a plurality of vacuum
chambers are provided in a connected form when it is set up as a
mass-production apparatus. Hence, the apparatus tends to have a large size
and, in particular, to be very long in the transport direction of a
belt-like member (substrate).
Thus, the apparatus for producing photovoltaic devices by the conventional
roll-to-roll system type plasma-assisted CVD tends to be very long in the
transport direction of the belt-like member. In addition, when attempting
to obtain photovoltaic performance with desired characteristics, processes
have been taken to raise the temperature of the belt-like member and to
change the temperature for the baking of the vacuum chambers in order to
remove impurities. However, the heat history due to the repetition of
thermal expansion caused by such processes and contraction caused by
cooling acts as stress in the vacuum chambers to bring about strain, in
particular, to cause cracks at portions having a low strength, and has a
possibility of causing a problem of leaking.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to solve the above
problems involved in conventional apparatus and to provide a
deposited-film-forming apparatus that makes stabler transport of a heated
belt-like member stabler and can mass-produce a thin film, in particular,
for photovoltaic devices, as a thin film having good uniformity in
characteristics and having fewer defects.
To achieve the above object, in the present invention, the
deposited-film-forming apparatus for producing a thin film, particularly
for photovoltaic devices, is constituted as described below.
The deposited-film-forming apparatus of the present invention is an
apparatus for forming deposited films while continuously passing a
belt-like member through the insides of a plurality of vacuum chambers
connected via connecting members and superposingly forming a plurality of
different thin films on the surface of the belt-like member by
plasma-assisted CVD, wherein the vacuum chambers are fixed to a stand for
supporting the vacuum chambers, and a mechanism for relaxing stress acting
in the transport direction of the belt-like member, generated in the
vacuum chambers by the action of expansion and contraction due to thermal
expansion of the vacuum chambers, is provided between each vacuum chamber
and each connecting member.
In the present invention, the mechanism for relaxing stress may be
constituted of an expansion-contraction absorbing mechanism that absorbs
the shift of the vacuum chamber. In such an instance, in the present
invention, the expansion-contraction absorbing mechanism may have a
bellows structure or a structure in which a plurality of O-rings made of
rubber are superposed.
In the present invention, the above connecting members may each be
constituted of a gas gate, thus a deposited-film-forming apparatus
especially suited for photovoltaic devices can be made.
In the present invention, as another mechanism for relaxing stress
generated in the apparatus, a sliding mechanism may be provided by which
the vacuum chamber itself can be readily moved. In such an instance, the
sliding mechanism may be formed of a warped member attached to a leg of
the vacuum chamber, or formed of a spherical member attached to a leg of
the vacuum chamber, or still formed of a wheel-like member attached to a
leg of the vacuum chamber.
In the present invention, the sliding mechanism may be constituted in such
a way that the shift of the vacuum chamber in a direction right-angled to
the transport direction of the belt-like member is limited by means of a
slide-limiting mechanism, and a lubricant may be provided at a part where
the sliding mechanism comes into contact with the stand.
In the present invention, among the vacuum chambers connected in plurality,
a vacuum chamber provided at the middle of the course in which the vacuum
chambers are connected and arranged in the transport direction may be
fixed to the stand.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view showing the deposited-film-forming
apparatus of the present invention.
FIG. 2 is a cross-sectional view showing an example of the
expansion-contraction absorbing mechanism.
FIGS. 3A and 3B are cross-sectional views showing examples of the
expansion-contraction absorbing mechanism.
FIG. 4 is a diagrammatic view showing an example of the sliding mechanism.
FIG. 5 is a diagrammatic view showing another example of the sliding
mechanism.
FIG. 6 is a diagrammatic view showing still another example of the sliding
mechanism.
FIG. 7 is a diagrammatic view showing a further example of the sliding
mechanism.
FIG. 8 is a diagrammatic view showing a still further example of the
sliding mechanism.
FIGS. 9A, 9B and 9C are cross-sectional views showing examples of the
photovoltaic device that can be produced by the deposited-film-forming
apparatus of the present invention.
FIG. 10 is a perspective view showing an example in which the belt-like
member is bent to form a cylindrical space forming a film.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
(1) Expansion-contraction absorbing mechanism:
FIG. 1 diagrammatically illustrates a roll-to-roll type film-forming
apparatus.
A roll-to-roll type film-forming apparatus 100 comprises as vacuum chambers
an unloading chamber 101, an n-type semiconductor layer deposition chamber
102, an i-type semiconductor layer deposition chamber 103, a p-type
semiconductor layer deposition chamber 104 and a winding chamber 105,
which are connected with each other through gas gates 106 as connecting
members. Each deposition chamber is provided with a heating infrared lamp
108. In the course where a belt-like member (hereinafter, often substrate)
110 is passed through the deposition chambers 102, 103 and 104, the
n-type, i-type and p-type semiconductor layers are successively formed. A
transparent conductive layer may be formed using an apparatus similarly
made up.
In each gas gate 106, scavenging gas is flowed from the upper part and
lower part (as shown by the arrows in FIG. 1) so that material gases in
the deposition chambers connected adjacently to each other are prevented
from being intermingled.
At a connecting zone for each chamber, an expansion-contraction absorbing
mechanism 107 is provided.
To deposit semiconductor layers in the respective deposition chambers,
microwave CVD, high-frequency wave CVD, thermal CVD, photo CVD or the like
is appropriately used. To deposit a metal oxide as a transparent
conductive layer, sputtering, resistance heat vacuum deposition,
electron-beam vacuum deposition or the like is used.
The expansion-contraction absorbing mechanism may be provided at every
position between the vacuum chambers fixed to a stand. With regard to a
vacuum chamber that requires no heating steps such as the heating of the
belt-like member and the baking of the vacuum chamber, the chamber may
either be provided or not be provided with the expansion-contraction
absorbing mechanism.
In the present invention, the vacuum chambers may be fixed to the stand by
a means such as bolt-fastening or welding. In view of the management of
maintenance made by disassembling and adjusting the vacuum chambers and
connecting members, the vacuum chambers may preferably be fixed in such a
manner that they can be relatively easily dismounted from and fixed to the
stand.
In the present invention, the expansion-contraction absorbing mechanism may
preferably be expandable and contractable by 30 mm and 60 mm,
respectively, at maximum in the transport direction of the belt-like
member, regarding as the starting point the position where the vacuum
chamber is stable at room temperature, and more preferably by 15 mm and 30
mm, respectively, as expansion-contraction distance.
In the present invention, the expansion-contraction absorbing mechanism
provided at the connecting zone may have a bellows structure capable of
expanding and contracting in the transport direction of the belt-like
member. This makes it possible to achieve the expansion-contraction
distance within the above ranges.
The bellows structure may be formed of a material appropriately selected
from metals such as Al, Ni, Ti, Mo, W, Fe, V, Cr and stainless steel,
taking account of its mechanical strength and easy processing.
The expansion-contraction absorbing mechanism may have a cross-sectional
shape which depends on the width of the belt-like member and the
cross-sectional shape of the connecting member. In view of easy
processing, it may have a rectangular, square, circular or oval cross
section.
The expansion-contraction absorbing mechanism can be made up utilizing
expansion-contraction properties of an O-ring.
In the present invention, the O-ring may be made of an elastic material
such as nitrile rubber, silicone rubber or fluorine rubber, any of which
may preferably be used.
The expansion-contraction distance can be determined by appropriately
selecting the rubber diameter of the O-ring. In usual instances, when the
O-ring has a diameter of 10 mm, the tolerance of expansion and contraction
of rubber while maintaining the function of vacuum sealing at the vacuum
chambers and connecting members is about 2 mm, and hence it is necessary
to use several O-rings superposed in order to achieve the above
expansion-contraction distance.
In this instance, as flanges used for superposing the O-rings, it is
possible to use a plurality of flanges of a "plane sheet form" and those
of a "groove form" having grooves to which O-rings are fitted.
Photovoltaic devices may be produced using the above apparatus of the
present invention for continuously producing photovoltaic devices. Thus,
the problems stated previously can be solved and also the belt-like member
continuously moved can be more stably transported.
In addition, this consequently makes it possible to produce photovoltaic
devices having a high quality and a good uniformity.
The expansion-contraction absorbing mechanism used in the present invention
will be described below in a specific manner.
FIG. 2 is a partially enlarged cross-sectional view of the apparatus
according to the present invention, and illustrates bellows members 21
serving as the expansion-contraction absorbing mechanism, attached to
every position between the respective vacuum chambers 101 to 105 and
connecting members.
In FIG. 2, the bellows member 21 functions as a cushioning mechanism that
relaxes the stress applied in the transport direction (as shown by an
arrow in FIG. 2) of a belt-like member 104 that is generated when each
vacuum chamber shifts from its original position upon thermal expansion
and contraction repeated in the transport direction. In FIG. 2, reference
numeral 22 denotes an O-ring for vacuum sealing.
FIG. 3A is a cross-sectional view of another the expansion-contraction
absorbing mechanism employing O-rings. In FIG. 3A, each O-ring is provided
between the vacuum chamber and the connecting member, and can relax the
stress generated when each vacuum chamber shifts in the transport
direction (as shown by an arrow in FIG. 3A) upon its expansion and
contraction.
As to the expansion-contraction distance of the O-ring, it is necessary to
ensure an expansion-contraction distance long enough to maintain the
vacuum of the vacuum chamber within the range of the expansion and
contraction of the vacuum chamber. Stated specifically, when the O-ring
has a diameter of 10 mm, the tolerance of expansion and contraction that
is necessary for maintaining the vacuum is 1 mm on the expansion side and
1 mm on the contraction side.
In order to ensure more expansion and contraction, as flanges for
superposing a plurality of O-rings as shown in FIG. 3B, a plurality of
flanges of a "plane sheet form" and those of a "groove form" having
grooves to which O-rings are fitted may be used. As the result, it is
possible to ensure expansion and contraction of, e.g., 10 mm on the
expansion side and 10 mm on the contraction side. The transport direction
of the belt-like member is shown by an arrow in FIG. 3A.
(2) Sliding mechanism:
Another method for relaxing the stress generated in the apparatus is to
provide a sliding mechanism that can shift the vacuum chamber itself with
ease. In the present invention, the mechanism of sliding the vacuum
chamber in the transport direction of the belt-like member may be provided
at all the vacuum chambers provided in a line in the transport direction.
Also, the middle-positioned vacuum chamber to which substantially no
stress is applied may be fixed to the stand.
According to the sliding mechanism of the present invention, the vacuum
chamber is brought into contact with the stand by point contact, line
contact or face contact without any fixing means such as bolt fastening or
welding. Further, a lubricant may be optionally used at the contact
portion so that the sliding mechanism can make the vacuum chamber more
readily shiftable.
In the present invention, a wheel-like rotary motion may be utilized so
that the sliding mechanism can make the vacuum chamber readily shiftable.
In this way, the vacuum chambers can freely shift in the transport
direction of the belt-like member.
Meanwhile, the vacuum chambers can be made slidable also in the direction
right-angled to the transport direction. In such an instance, it is
preferable to provide a mechanism for appropriately limiting over-sliding
also in order to make the arrangement of the vacuum chambers stable.
In the present invention, the mechanism for appropriately limiting
over-sliding comprises guides provided in parallel to the transport
direction of the belt-like member so as to serve as a barrier for limiting
any excessive shift of the vacuum chamber when it shifts to the direction
right-angled to the transport direction.
The sliding mechanism of the present invention will be described below in a
specific manner.
FIG. 4 is a partial diagrammatic view of the apparatus of the present
invention, provided with a sliding mechanism comprising a warped member 41
fixed to each of legs at the bottom four corners of the vacuum chamber.
As shown in FIG. 4, the warped member is upward warped at its edges in the
direction vertical to the transport direction of the belt-like member 43
so that it can decrease the friction with a stand 42 when the vacuum
chamber shifts while repeating thermal expansion and contraction.
Among the vacuum chambers 40 arranged in a line in the transport direction
of the belt-like member 43, the vacuum chamber disposed at the middle may
be fixed to the stand 42.
The warped member 41 and the stand 42 may be formed mainly of a material
appropriately selected from metals such as Al, Ni, Ti, Mo, W, Fe, V, Cr
and stainless steel, taking account of their mechanical strength and easy
processing.
With regard to the surface properties of the warped member and stand, they
may preferably have mirror surfaces finished by buffing. A lubricant may
also be applied to the contact surfaces in order to more decrease the
friction with the stand 42.
FIG. 5 diagrammatically illustrates another example of the sliding
mechanism. In FIG. 5, as the sliding mechanism, spherical sliding members
51 are attached to legs 50 of the vacuum chamber (not shown), and come
into point contact with a stand 52 to make the vacuum chamber smoothly
shiftable.
FIG. 6 shows still another example of the sliding mechanism according to
the present invention. As shown in FIG. 6, the sliding mechanism is
constituted of wheels 61 and makes a vacuum chamber 60 smoothly shiftable
on a stand 62 in the transport direction of the belt-like member 63.
FIG. 7 is a diagrammatic view showing a slide-limiting mechanism 72. As
shown in FIG. 7, it limits the sliding direction of sliding members 71
which correspond to the spherical sliding members 51 described above.
Members constituting the slide limiting mechanism 72 are provided in
parallel to the belt-like member transport direction (as shown by an arrow
in FIG. 7), and the mechanism is so constructed that each vacuum chamber
(not shown) does not drop off a stand 73 and also the vacuum chambers
connected and arranged in the belt-like member transport direction are
limited on their shift in the direction right-angled to the transport
direction. The sliding mechanism 71 is attached to each of legs 70 of the
vacuum chamber (not shown).
FIG. 8 diagrammatically illustrates still another example of the sliding
mechanism according to the present invention. As shown in FIG. 8, rails 82
are provided on a stand 80 in parallel to the belt-like member transport
direction. Also, wheels 81 attached to legs 83 of the vacuum chamber (not
shown) are made smoothly movable on the track of the rails 82.
Belt-like Member
The belt-like member preferably used in the present invention may
preferably be made of a material that may cause less deformation and
strain at the temperature required at the time of the formation of
semiconductor layers, has a desired strength and has a conductivity.
Stated specifically, it may be formed of a thin sheet of a metal such as
stainless steel, aluminum and alloys thereof, iron and alloys thereof and
copper and alloys thereof, and a composite material of such sheets, and
any of these materials having thin metallic films of different materials
and/or insulating thin films of SiO.sub.2, Si.sub.3 N.sub.4, Al.sub.2
O.sub.3, AlN or the like formed on the surface by surface coating
treatment such as sputtering, vacuum deposition or plating.
The belt-like member may also be formed of a sheet made of a heat-resistant
resin such as polyimide, polyamide, polyethylene terephthalate or epoxy
resin, or a composite of any of these with glass fiber, carbon fiber,
boron fiber, metallic fiber or the like, whose surface has been subjected
to conductive treatment by plating, vacuum deposition, sputtering or
coating of a single metal or an alloy thereof or a transparent conductive
oxide (TCO).
The belt-like member may have a thickness as small as possible taking
account of cost and stock space and so long as it exhibits a strength
enough to maintain a curved shape when it is transported by the transport
means. Stated specifically, it may preferably have a thickness of from
0.01 mm to 5 mm, more preferably from 0.02 mm to 2 mm, and most preferably
from 0.05 mm to 1 mm. Use of the thin sheet of a metal or the like makes
it easy to obtain the desired strength even if its thickness is made
smaller.
The belt-like member may have any width without any particular limitations,
depending on the means for forming semiconductor layers and the size of
chambers therefor.
The belt-like member may have any length without any particular
limitations, and may have such a length that it can be wound up into a
roll. Sheets with a continuous length may be connected by welding or the
like so as to be made more continuous.
In the case when the belt-like member is made of an electrically conductive
material such as a metal, it may be made to serve as an electrode for
directly taking out electric currents. In the case when it is made of an
electrically insulating material such as a synthetic resin, it may
preferably be beforehand subjected to surface treatment on the side where
the semiconductor layers are formed, by a process such as plating, vacuum
deposition or sputtering of a single metal or an alloy thereof or a
transparent conductive oxide (TCO), such as Al, Ag, Pt, Au, Ni, Ti, Mo, W,
Fe, V, Cr, Cu, stainless steel, brass, Nichrome, SnO.sub.2 In.sub.2
O.sub.3, ZnO, SnO.sub.2 -In.sub.2 O.sub.3 (ITO) to prepare an electrode
for taking out electric currents.
In the case when the belt-like member is made of a non-light-transmitting
material such as a metal, a reflective conductive film for improving
reflectance of long-wavelength light on the substrate surface may
preferably be formed on the belt-like member. The reflective conductive
film may be formed of a material including Ag, Al and Cr as materials
preferably used.
For the purposes of, e.g., preventing constituent elements from mutually
diffusing between the substrate material and the semiconductor layers and
providing a buffer layer for preventing short circuit, a metal layer or
the like may preferably be provided as the reflective conductive film on
the substrate at its side where the semiconductor layers are formed.
The buffer layer may be formed of a material including ZnO as a material
preferably used.
When the belt-like member is relatively transparent and a solar cell has
such a layer configuration that the light is made incident on the
belt-like member side, a conductive thin film such as the above
transparent conductive oxide or metal thin film may preferably be
beforehand formed by deposition.
As surface properties of the belt-like member, it may have a smooth surface
or may have a surface with fine irregularities. In the case when it has a
surface with fine irregularities, the irregularities may be spherical,
conical or pyramidal, and may preferably have a maximum height (Rmax) of
from 500 A to 5,000 A, whereby the reflection of light on the surface can
be made irregular to bring about an increase in light-path length of the
light reflected on the surface.
Gas Gate
The gas gate of the deposited film-forming apparatus of the present
invention will be described below.
In the present invention, a gas gate means is preferably used to separate
and isolate the vacuum chambers for feeding and winding up the belt-like
member from the vacuum chambers for forming semiconductor layers and to
allow the belt-like member to pass through these chambers so as to be
continuously transported.
The gas gate means is required to have the ability not to mutually diffuse
atmospheres formed by semiconductor layer material gases used, due to a
pressure difference generated between the respective chambers.
As its basic concept, the gas gate means disclosed in U.S. Pat. No.
4,438,723 may be employed. Its ability, however, must be improved.
Stated specifically, the gas gate means is required to withstand a pressure
difference of about 10.sup.6 times at maximum, and an oil diffusion pump,
a turbo molecular pump, a mechanical booster pump or the like, having a
large exhaust capacity, may preferably be used as an exhaust pump.
The gas gate may have a cross-sectional shape of a slit, or a shape similar
thereto, and its size may be calculated and designed using a usual
expression of conductance calculation, in conformity with its whole length
and the discharge capacity of the discharge pump. In order to more improve
the ability of separation, a gate gas may preferably be used in
combination, which may include, e.g., rare gases such as Ar, He, Ne, Kr,
Xe and Rn or dilute gases for forming semiconductor layers, such as
H.sub.2.
The flow rate of the gate gas may be appropriately determined according to
the conductance of the whole gas gate and the capacity of the exhaust pump
used. For example, when a point at which the pressure becomes maximum is
set at substantially the middle of a gas gate, the gate gas flows from the
middle of the gas gate to both vacuum chamber sides, so that the mutual
gas diffusion between the both-side chambers can be made a minimum.
In practice, the amount of the diffused gases may be measured using a mass
analyzer or the semiconductor layer formed may be compositionally
analyzed, to thereby determine optimum conditions.
Photovoltaic Device
FIGS. 9A to 9C are diagrammatic views showing examples of the constitution
of the photovoltaic device that can be produced by the apparatus of the
present invention.
The example shown in FIG. 9A is constituted of a belt-like member 901, a
lower electrode 902, a semiconductor layer 903 having a first conductivity
type (hereinafter "first-conductivity type layer"), an i-type
semiconductor layer (hereinafter "i-type layer") 904, a semiconductor
layer 905 having a second conductivity type (hereinafter
"second-conductivity type layer"), an upper electrode 906, and a collector
electrode 907.
The example shown in FIG. 9B is what is called a tandem type (or double
type) photovoltaic device made up by superposing two Sets of photovoltaic
devices employing as i-type layers two semiconductor layers having
different bandgap and/or layer thickness, and is constituted of a
belt-like member 901, a lower electrode 902, a first-conductivity type
layer 903, an i-type layer 904, a second-conductivity type layer 905, a
first-conductivity type layer 903, an i-type layer 904, a
second-conductivity type layer 905, an upper electrode 906, and a
collector electrode 907.
The example shown in FIG. 9C is what is called a triple type photovoltaic:
device made up by superposing three sets of photovoltaic devices employing
as i-type layers three semiconductor layers having different bandgap
and/or layer thickness, and is constituted of a belt-like member 901, a
lower electrode 902, a first-conductivity type layer 903, an i-type layer
904, a second-conductivity type layer 905, a first-conductivity type layer
903, an i-type layer 904, a second-conductivity type layer 905, a
first-conductivity type layer 903, an i-type layer 904, a
second-conductivity type layer 905, an upper electrode 906, and a
collector electrode 907.
The constitution of the photovoltaic devices will be described below.
As the belt-like member 901 used in the present invention, a member made of
a flexible material may preferably be used, which may be either
electrically conductive or electrically insulating. Such materials may
also be either light-transmittive or non-light-transmittive. In the case
when light is made incident on the side of the belt-like member 901, the
material must of course be light-transmittive.
Stated specifically, the belt-like member may include the belt-like member
previously described as used in the present invention. Use of such a
belt-like member can make the photovoltaic devices produced light-weight,
make their strength higher and make their transport space smaller.
As the electrode of the photovoltaic device, the belt-like member can serve
also as the lower electrode in the case when the belt-like member 901 is
electrically conductive. However, when belt-like member 901 is
electrically conductive but has a high sheet resistivity, the lower
electrode 902 may be provided as a low-resistance electrode for taking out
electric currents or for the purposes of enhancing reflectance and
effectively utilizing incident light.
Materials for the electrode may include metals such as Ag, Au, Pt, Ni, Cr,
Cu, Al, Ti, Zn, Mo and W or alloys of these. Thin films of any of these
metals may be formed by vacuum deposition, electron beam deposition,
sputtering or the like.
Care must also be taken so that the metal thin films formed do not serve as
resistance components against the output of the photovoltaic device, and
may preferably have a sheet resistivity of 50 .OMEGA. or less, and more
preferably 10 .OMEGA. or less.
Not shown in FIGS. 9A to 9C, a buffer layer for preventing short circuits
and preventing diffusion, formed of, e.g., ZnO, may be provided between
the lower electrode 902 and the first-conductivity type layer 903. The
buffer layer can be effective for, e.g., not only preventing metal
elements constituting the lower electrode 902, from diffusing into the
first-conductivity type layer 903, but also, when a slight resistivity is
imparted thereto, preventing short circuits from being caused by defects
such as pinholes between the lower electrode 902 and the upper electrode
transparent electrode 906 which are provided interposing the semiconductor
layers, and also entrapping the light made incident on the device inside
the photovoltaic device by causing multiple interference due to the thin
film.
The transparent electrode 906 constituting the upper electrode used in the
present invention may preferably have a light transmittance of 85% or more
so that the light transmitted from the sun or white fluorescent lamps can
be absorbed in the semiconductor layers in a good efficiency. It may also
have a sheet resistivity of 100 .OMEGA. or less so that it does not
electrically serve as a resistance component against the output of the
photovoltaic device.
Materials having such properties may include metal oxides such as
SnO.sub.2, In.sub.2 O.sub.3, ZnO, CdO, Cd.sub.2 SnO.sub.4, ITO (In.sub.2
O.sub.3 +SnO.sub.2) and metals such as Au, Al and Cu, which may be formed
into very thin and semitransparent films to obtain metal thin films.
In the examples shown in FIGS. 9A to 9C, the transparent electrode is;
formed on the second-conductivity type layer 905, and hence materials
having a good mutual adhesion must be selected. Such an electrode can be
formed by resistance heating vacuum deposition, electron beam heating
vacuum deposition, sputtering, spraying or the like, any of which may be
selected as desired.
The collector electrode 907 used in the present invention is provided on
the transparent electrode 906 so that the surface resistivity of the
transparent electrode 906 can be made lower.
Materials for the collector electrode may include thin films of metals such
as Ag, Cr, Ni, Al, Ag, Au, Ti, Pt, Cu, Mo and W or alloys of these. Such
thin films may be superposingly formed.
The shape and area of the electrode may be appropriately designed so that
the amount of light incident on the semiconductor layers can be ensured.
For example, the electrode may have such a shape that it uniformly extends
over the light-receiving surface of the photovoltaic device and also has
an area percentage of 15% or less, and more preferably 10% or less, with
respect to the area of the light-receiving surface.
It may also preferably have a sheet resistivity of 50 .OMEGA. or less, and
more preferably 10 .OMEGA. or less.
First- and Second-conductivity Type Layers
As materials used for the first- and second-conductivity type layers in the
photovoltaic device of the present invention, non-single-crystal
semiconductors comprising one or more atoms belonging to Group IV of the
Periodic Table are suitable.
For the conductivity type layer on the side irradiated with light,
microcrystallized semiconductors are most suitable. Such microcrystals may
have grain diameters of from 3 nm to 20 nm, and most preferably from 3 nm
to 10 nm.
In the case when the first- or second-conductivity type layer has an
n-type, elements belonging to Group V of the Periodic Table are suitable
as additives to be incorporated into the first- or second-conductivity
type layer. In particular, phosphorus (P), nitrogen (N), arsenic (As) and
antimony (Sb) are most suitable.
In the case when the first- or second-conductivity type layer has a p-type,
elements belonging to Group III of the Periodic Table are suitable as
additives to be incorporated into the first- or second-conductivity type
layer. In particular, boron (B), aluminum (Al) and gallium (Ga) are most
suitable.
The first- and second-conductivity type layers may each preferably have a
layer thickness of from 1 nm to 50 nm, and most preferably from 3 nm to 10
nm.
In addition, in order to decrease the absorption of light more in the
conductivity type layer on the side irradiated with light, it is
preferable to use a semiconductor layer having a bandgap larger than the
bandgap of the semiconductor constituting the i-type layer. For example,
when the i-type layer comprises amorphous silicon, it is most suitable to
use non-single-crystal silicon carbide in the conductivity type layer on
the side irradiated with light.
i-Type Layer
Semiconductor materials used in the i-type layer in the photovoltaic device
of the present invention may include semiconductors comprised of one or
more of atoms belonging to Group IV of the Periodic Table, such as Si, Ge,
C, SiC, GeC, SiSn, GeSn and SnC. As Group III-V compound semiconductors,
they may include GaAs, GaP, GaSb, InP, InAs; as Group II-VI compound
semiconductors, ZnSe, ZnS, ZnTe, CdS, CdSe and CdTe; as Group I-III-VI
compound semiconductors, CuAlS.sub.2, CuAlSe.sub.2, CuAlTe.sub.2,
CuInSe.sub.2, CuInSe.sub.2, CuInTe.sub.2, CuGaAs.sub.2, CuGaSe.sub.2,
CuGaTe, AgInSe.sub.2, AgInTe.sub.2 ; and as Group II-IV-V compound
semiconductors, ZnSiP.sub.2, ZnGeAs.sub.2, CdSiAs.sub.2, CdSnP.sub.2 ; and
as oxide semiconductors, Cu.sub.2 O, TiO.sub.2, In.sub.2 O.sub.3,
SnO.sub.2, ZnO, CdO, Bi.sub.2 O.sub.3 and CdSnO.sub.4.
When the photovoltaic devices are produced using the apparatus of the
present invention as described above, the problems discussed previously
can be solved and also the various requirements stated previously can be
satisfied, and photovoltaic devices having a high quality and a good
uniformity and having less defects can be produced on the belt-like member
continuously transported.
A light-transmittive substrate may be used as the belt-like member 901 so
that light is made incident on the substrate side. In such an instance,
the electrode 902 may be a transparent electrode formed of ITO or the
like, and the second electrode 906 may be formed of a metal.
The apparatus of the present invention for continuously producing
photovoltaic devices will be further described below by giving Examples.
The present invention is by no means limited by these Examples.
EXAMPLE 1
In the apparatus as shown in FIG. 1, the vacuum chambers 101, 102, 103, 104
and 105 were all fixed to the stand, and then expansion-contraction
absorbing members 21 as shown in FIG. 2 were attached to positions between
the connecting zones of gas gates and the respective vacuum chambers.
Using this apparatus, photovoltaic devices were produced in the following
way.
First, a bobbin wound up with a belt-like member 110 made of SUS30BA
stainless steel (120 mm wide, 200 m long and 0.13 mm thick) having been
well degreased and cleaned and on which a silver thin film 100 nm thick
and a ZnO thin film 1 .mu.m thick had been vacuum-deposited as the lower
electrode by sputtering was set in a vacuum chamber 101 having a substrate
feed mechanism. The belt-like member 110 was passed through a deposition
chamber 102 for forming an n-type layer, a deposition chamber 103 for
forming an i-type layer and a deposition chamber 104 for forming a p-type
layer, up to a vacuum chamber 105 having a belt-like member winding
mechanism, and its tension was adjusted so that the belt-like member was
not slack.
Now, each vacuum chamber was evacuated to a vacuum of 1.times.10.sup.-6
Torr or less by means of a vacuum pump (not shown). Next, the gate gas of
H.sub.2 at 700 sccm was flowed into each gas gate 106, and the belt-like
member 110 was heated to 350.degree. C. in the chambers 102, 103 and 104
by means of heating infrared lamps 108. Under conditions as shown in Table
1, n-, i- and p-type layers were formed. Thereafter, ITO and Al were
vacuum-deposited to form a transparent electrode and a collector
electrode, respectively.
In Table 1, the first-conductivity type layer was an n-type layer, and the
second-conductivity type layer was a p-type layer.
The extent of shift of each vacuum chamber, affected by thermal expansion
due to the plasma discharge and heating with lamp heaters in the vacuum
chambers was measured. Here, the extent of contraction occurring when the
expansion-contraction absorbing members 21 (the expansion-contraction
absorbing mechanism 107) attached to the respective vacuum chambers were
heated was measured regarding as the starting point the position of each
member standing at room temperature. Also, since the temperature of each
vacuum chamber reached a maximum point immediately before the plasma
discharge was stopped and the extent of shift of each vacuum chamber
became maximum at that point of time, the maximum extent of contraction of
each expansion-contraction absorbing member 21 was defined to be the
extent of contraction at this point of time.
As a result of this measurement, the expansion-contraction absorbing
members 21 of the vacuum chambers were seen to have shrunk by 5 mm each.
When the vacuum chambers were cooled to room temperature, the extent of
contraction of these members became zero, and these expansion-contraction
absorbing members had returned to their original positions.
COMPARATIVE EXAMPLE 1
The expansion-contraction absorbing members 21 as described above were all
detached and the vacuum chambers were all fixed to the stand, where
photovoltaic devices (Comp. 1 devices) were produced under entirely the
same film-forming conditions as in Example 1.
The extent of shift of each vacuum chamber, affected by thermal expansion
due to the plasma discharge in each vacuum chamber and the heating with
lamp heaters was measured in the same manner as in Example 1.
It was just like Example 1 that the temperature of each vacuum chamber
reached a maximum point immediately before the plasma discharge was
stopped. However, while in Example 1 the extent of contraction of each
expansion-contraction absorbing member 21 reached a maximum (5 mm) at this
point of time, the extent of shift of each vacuum chamber in this
Comparative Example 1 was, as a result of measurement, 0.5 mm in respect
of the vacuum chambers 102 and 104 and 1 mm in respect of the vacuum
chambers 101 and 105, which respectively shifted in the direction they
went away from the vacuum chamber 103 provided at the middle.
When the vacuum chambers were well cooled to room temperature, the extent
of shift of these chambers became zero, and the respective vacuum chambers
returned to their original positions.
EVALUATION ON EXAMPLE 1 AND COMPARATIVE EXAMPLE 1
The uniformity of characteristics and density of defects in the
photovoltaic devices produced in Example 1 (Ex. 1 devices) and Comparative
Example 1 (Comp. 1 devices) were evaluated.
To evaluate the uniformity of characteristics, the photovoltaic devices
produced in Example 1 (Ex. 1 devices) and Comparative Example 1 (Comp. 1
devices), formed on the belt-like member, were cut out at intervals of 10
m in a size 5 cm square, and placed under irradiation with light of AM-1.5
(100 mW/cm.sup.2) to measure their photoelectric conversion efficiency.
Any scattering of the measurement results of the photoelectric conversion
efficiency was examined. Regarding the results on the photovoltaic devices
of Comparative Example 1 (Comp. 1 devices) as a standard, reciprocals of
the degree of scattering were calculated to obtain the results as shown in
Table 2.
To evaluate the defect density, 100 pieces of the photovoltaic devices
produced in Example 1 (Ex. 1 devices) and Comparative Example 1 (Comp. 1
devices), formed on the belt-like member, were cut out in a size 5 cm
square within the length 5 m at the middle portion thereof, and electric
currents in the reverse direction were measured to detect the presence or
absence of defects (imperfections) in the respective photovoltaic devices.
Regarding the results on the photovoltaic devices of Comparative Example 1
(Comp. 1 devices) as a standard, reciprocals of the number of defects were
calculated to obtain the results as shown in Table 2.
It can be said that the higher the numerical values of these are, the
better the solar cells (photovoltaic devices) are on the whole in respect
of both the defect density and the uniformity of characteristics.
In Table 2, the uniformity of characteristics and defect density are
indicated as relative values with respect to those of Comparative Example
1 regarded as a standard.
As is seen from Table 2, the photovoltaic devices of Example 1 (Ex. 1
devices) show good results with respect to both the uniformity of
characteristics and the defect density, compared with the photovoltaic
devices of Comparative Example 1 (Comp. 1 devices), proving that the
present invention is effective.
EXAMPLE 2
Tandem type solar cells (photovoltaic devices) as shown in FIG. 9B were
produced, having two sets of pin junctions comprised of a
first-conductivity type layer, an i-type layer, a second-conductivity type
layer, a first-conductivity type layer, an i-type layer and a
second-conductivity type layer which were superposed on the lower
electrode.
The i-type layers were respectively formed of amorphous silicon germanium
in the first pin junction, and amorphous silicon in the second pin
junction.
The photovoltaic devices were produced under conditions as shown together
in Table 3.
In Table 3, the first-conductivity type layer was an n-type layer, and the
second-conductivity type layer was a p-type layer. Layers were superposed
in the order of the upper to lower columns as shown in the table.
In the present Example, the vacuum chambers for forming semiconductor
layers were all fixed to the stand, and then expansion-contraction
absorbing members 21 as shown in FIG. 2 were attached to positions between
the connecting zones between gas gates and the respective vacuum chambers,
thus the photovoltaic devices were produced.
Using the apparatus set up in this way, the tandem type solar cells were
produced according to the same process for producing photovoltaic devices
as in Example 1.
The extent of contraction of each expansion-contraction absorbing member,
affected by thermal expansion due to the plasma discharge and heating with
lamp heaters in the vacuum chambers was measured in the same manner as in
Example 1. Here, the extent of shift occurring when the vacuum chambers
were heated was measured regarding as the starting point the position of
each vacuum chamber standing at room temperature. Also, the temperature of
each vacuum chamber reached a maximum point immediately before the plasma
discharge was stopped and the extent of shift of each vacuum chamber
reached a maximum at that point of time, where the extent of contraction
of each expansion-contraction absorbing member also reached maximum.
As a result of this measurement, the expansion-contraction absorbing
members provided between the vacuum chambers and the connecting members
(gas gates) were all seen to have shrunk by 5 mm each.
When the vacuum chambers were cooled to room temperature, the extent of
contraction of these members became zero, and these expansion-contraction
absorbing members returned to their original positions.
COMPARATIVE EXAMPLE 2
The expansion-contraction absorbing members 21 as described above were all
detached and the vacuum chambers were all fixed to the stand, where
photovoltaic devices (Comp. 2 devices) were produced under entirely the
same film-forming conditions as in Example 2.
The extent of shift of each vacuum chamber, affected by thermal expansion
due to the plasma discharge in each vacuum chamber and the heating with
lamp heaters was measured in the same manner as in Example 2.
It was just like Example 2 that the temperature of each vacuum chamber
reached a maximum point immediately before the plasma discharge was
stopped. However, while in Example 2 the extent of contraction of each
expansion-contraction absorbing member, i.e., the extent of shift of each
vacuum chamber became maximum (5 mm) at this point of time, the extent of
shift of each vacuum chamber in this Comparative Example 2 was, as a
result of measurement, about 0.5 mm in respect of all the vacuum chambers.
When the vacuum chambers were well cooled to room temperature, the extent
of shift of these chambers became zero, and the respective vacuum chambers
were seen to have returned to original positions.
EVALUATION ON EXAMPLE 2 AND COMPARATIVE EXAMPLE 2
The uniformity of characteristics and density of defects in the
photovoltaic devices produced in Example 2 (Ex. 2 devices) and Comparative
Example 2 (Comp. 2 devices) were evaluated.
To evaluate the uniformity of characteristics, the photovoltaic devices
produced in Example 2 (Ex. 2 devices) and Comparative Example 2 (Comp. 2
devices), formed on the belt-like member, were cut out at intervals of 10
m in a size 5 cm square, and placed under irradiation by light of AM-1.5
(100 mW/cm.sup.2) to measure their photoelectric conversion efficiency.
Any scattering of the measurement results of the photoelectric conversion
efficiency was examined. Regarding the results on the photovoltaic devices
of Comparative Example 2 (Comp. 2 devices) as a standard, reciprocals of
the degree of scattering were calculated to obtain the results as shown in
Table 4.
To evaluate the defect density, 100 pieces of the photovoltaic devices
produced in Example 2 (Ex. 2 devices) and Comparative Example 2 (Comp. 2
devices), formed on the belt-like member, were cut out in a size 5 cm
square within the length 5 m at the middle portion thereof, and electric
currents in the reverse direction were measured to detect the presence or
absence of defects (imperfections) in the respective photovoltaic devices.
Regarding the results on the photovoltaic devices of Comparative Example 2
(Comp. 2 devices) as a standard, reciprocals of the number of defects were
calculated to obtain the results as shown in Table 4.
In Table 4, the uniformity of characteristics and defect density are
indicated as relative values with respect to those of Comparative Example
2 regarded as a standard.
As is seen from Table 4, the photovoltaic devices of Example 2 (Ex. 2
devices) show good results with respect to both the uniformity of
characteristics and the defect density, compared with the photovoltaic
devices of Comparative Example 2 (Comp. 2 devices), proving that the
present invention is effective.
EXAMPLE 3
Triple type photovoltaic devices as shown in FIG. 9C were produced, having
three sets of pin junctions of first-conductivity type layers, i-type
layers and second-conductivity type layers which were superposed on the
lower electrode.
The i-type layers were respectively formed of amorphous silicon germanium
in the first pin junction, amorphous silicon germanium in the second pin
junction, and amorphous silicon in the third pin junction.
The photovoltaic devices were produced under conditions as shown together
in Table 5.
In Table 5, the first-conductivity type layer was an n-type layer, and the
second-conductivity type layer was a p-type layer. Layers were superposed
in the order of the upper to lower columns as shown in the table.
In the present Example, the vacuum chambers for forming semiconductor
layers were all fixed to the stand, and then expansion-contraction
absorbing members as shown in FIG. 3B were attached to the connecting
zones between gas gates and the respective vacuum chambers, thus the
photovoltaic devices were produced.
Using the apparatus set up in this way, the triple type solar cells were
produced according to the same process for producing photovoltaic devices
as in Example 2.
The extent of contraction of each expansion-contraction absorbing member,
affected by thermal expansion due to the plasma discharge and heating with
lamp heaters in the vacuum chambers was measured in the same manner as in
Example 1. Here, the extent of shift occurring when the vacuum chambers
were heated was measured regarding as the starting point the position of
each vacuum chamber standing at room temperature. Also, the temperature of
each vacuum chamber reached a maximum point immediately before the plasma
discharge was stopped and the extent of shift of each vacuum chamber
became maximum at that point of time, where the extent of contraction of
each expansion-contraction absorbing member also became maximum.
As a result of this measurement, the expansion-contraction absorbing
members provided between the vacuum chambers and the connecting members
(gas gates) were all seen to have shrunk by 5 mm each. When the vacuum
chambers were cooled to room temperature, the extent of contraction of
these members became zero, and these expansion-contraction absorbing
members returned to their original positions.
COMPARATIVE EXAMPLE 3
The expansion-contraction absorbing members as used in Example 3 were all
detached and the vacuum chambers were all fixed to the stand, where
photovoltaic devices (Comp. 3 devices) were produced under entirely the
same film-forming conditions as in Example 3.
The extent of shift of each vacuum chamber, affected by thermal expansion
due to the plasma discharge in each vacuum chamber and the heating with
lamp heaters was measured in the same manner as in Example 1.
It was just like Example 3 that the temperature of each vacuum chamber
reached a maximum point immediately before the plasma discharge was
stopped. However, while in Example 3 the extent of contraction of each
expansion-contraction absorbing member, i.e., the extent of shift of each
vacuum chamber reached a maximum (5 mm) at this point of time, the extent
of shift of each vacuum chamber in this Comparative Example 3 was, as a
result of measurement, about 0.5 mm or about 0.6 mm even at the maximum in
respect of all the vacuum chambers.
When the vacuum chambers were cooled to room temperature, the extent of
shift of these chambers became zero, and the respective vacuum chambers
returned to their original positions.
EVALUATION ON EXAMPLE 3 AND COMPARATIVE EXAMPLE 3
The uniformity of characteristics and density of defects in the
photovoltaic devices produced in Example 3 (Ex. 3 devices) and Comparative
Example 3 (Comp. 3 devices) were evaluated.
To evaluate the uniformity of characteristics, the photovoltaic devices
produced in Example 3 (Ex. 3 devices) and Comparative Example 3 (Comp. 3
devices), formed on the belt-like member, were cut out at intervals 10 m
in a size 5 cm square, and placed under irradiation by light of AM-1.5
(100 mW/cm.sup.2) to measure their photoelectric conversion efficiency.
Any scattering of the measurement results of the photoelectric conversion
efficiency was examined. Regarding the results on the photovoltaic devices
of Comparative Example 3 (Comp. 3 devices) as a standard, reciprocals of
the degree of scattering were calculated to obtain the results as shown in
Table 6.
To evaluate the defect density, 100 pieces of the photovoltaic devices
produced in Example 3 (Ex. 3 devices) and Comparative Example 3 (Comp. 3
devices), formed on the belt-like member, were cut out in a size 5 cm
square within the length 5 m at the middle portion thereof, and electric
currents in the reverse direction were measured to detect the presence or
absence of defects (imperfections) in the respective photovoltaic devices.
Regarding the results on the photovoltaic devices of Comparative Example 3
(Comp. 3 devices) as a standard, reciprocals of the number of defects were
calculated to obtain the results as shown in Table 6.
In Table 6, the uniformity of characteristics and defect density are
indicated as relative values with respect to those of Comparative Example
3 regarded as a standard.
As is seen from Table 6, the photovoltaic devices of Example 3 (Ex. 3
devices) show good results with respect to both the uniformity of
characteristics and the defect density, compared with the photovoltaic
devices of Comparative Example 3 (Comp. 3 devices), proving that the
present invention is effective.
EXAMPLE 4
An example will be described below in which the photovoltaic devices are
produced while making up film-forming space by bending the belt-like
member in a cylindrical form in its transport direction inside the
deposition chambers 102, 103 and 104 shown in FIG. 1.
In FIG. 10, reference numeral 1001 denotes a belt-like member, which is
transported in the direction of a wide arrow shown in FIG. 10, and
continuously makes up film-forming space 1016 while keeping a
cylindrically curved shape by means of a supporting-transporting roller
1002 and 1003 and supporting-transporting rings 1004 and 1005.
Reference numerals 1006a to 1006e denote members constituting a temperature
control mechanism for heating or cooling the belt-like member 1001, which
are each independently temperature-controlled. In the present apparatus,
microwave applicators 1007 and 1008 are opposingly provided in pair. At
end portions thereof, microwave transmitting members 1009 and 1010 are
respectively provided, and rectangular waveguides 1011 and 1012 are also
respectively provided in such a way that the planes containing their long
sides are not vertical with respect to the planes containing the axes of
the supporting-transporting rollers and also the planes containing the
long sides are not parallel to each other.
In FIG. 10, for the purpose of illustration, the microwave applicator 1007
is shown in the state it is separated from the supporting-transporting
ring 1004. When deposited films are formed, it is provided in the
direction of a fine arrow shown in FIG. 10.
Reference numerals 1013a, 1013b and 1013c denote gas feed means, through
which material gases are introduced into the film-forming space by means
of gas feed equipment (not shown). The supporting-transporting rollers
1002 and 1003 are each internally provided with a transport speed
detecting mechanism (not shown) and a tension detecting control mechanism
(not shown) so that the transport speed of the belt-like member 1001 can
be kept constant and also the curved shape thereof can be kept constant.
Using this microwave CVD apparatus, photovoltaic devices were produced
under conditions as shown in Table 7.
In Table 7, the first-conductivity type layer was an n-type layer, and the
second-conductivity type layer was a p-type layer. Layers were superposed
in the order of the upper to lower columns as shown in the table.
In the present Example, the vacuum chambers for forming semiconductor
layers were all fixed to the stand, and then expansion-contraction
absorbing members 21 as shown in FIG. 2 were attached to positions between
the connecting zones between gas gates and the respective vacuum chambers,
thus the photovoltaic devices were produced.
The extent of contraction of each expansion-contraction absorbing member,
affected by thermal expansion due to the plasma discharge and heating with
lamp heaters in the vacuum chambers was measured in the same manner as in
Example 1. Here, the extent of contraction occurring when the
expansion-contraction absorbing members attached to the respective vacuum
chambers were heated was measured regarding as the starting point the
position of each member standing at room temperature. Also, since the
temperature of each vacuum chamber reached a maximum point immediately
before the plasma discharge was stopped and the extent of shift of each
vacuum chamber became maximum at that point of time, the maximum extent of
contraction of each expansion-contraction absorbing member was defined to
be the extent of contraction at this point of time.
As a result of this measurement, the expansion-contraction absorbing
members of the vacuum chambers were seen to have shrunk by 5 mm each. When
the vacuum chambers were cooled to room temperature, the extent of
contraction of these members became zero, and these expansion-contraction
absorbing members returned to their original positions.
COMPARATIVE EXAMPLE 4
The expansion-contraction absorbing members as used in Example 4 were all
detached and the vacuum chambers were all fixed to the stand, where
photovoltaic devices (Comp. 4 devices) were produced under entirely the
same film-forming conditions as in Example 4.
The extent of shift of each vacuum chamber, affected by thermal expansion
due to the plasma discharge in each vacuum chamber and the heating with
lamp heaters was measured in the same manner as in Example 4.
It was just like Example 4 that the temperature of each vacuum chamber
reached a maximum point immediately before the plasma discharge was
stopped. However, while in Example 4 the extent of contraction of each
expansion-contraction absorbing member reached maximum (5 mm) at this
point of time, the extent of shift of each vacuum chamber in this
Comparative Example 4 was, as a result of measurement, 0.5 mm in respect
of the vacuum chambers 102 and 104 and 1 mm in respect of the vacuum
chambers 101 and 105, which respectively shifted in the direction they
went away from the vacuum chamber 103 provided at the middle.
When the vacuum chambers were cooled to room temperature, the extent of
shift of these chambers became zero, and the respective vacuum chambers
returned to their original positions.
EVALUATION ON EXAMPLE 4 AND COMPARATIVE EXAMPLE 4
The uniformity of characteristics and density of defects in the
photovoltaic devices produced in Example 4 (Ex. 4 devices) and Comparative
Example 4 (Comp. 4 devices) were evaluated.
To evaluate the uniformity of characteristics, the photovoltaic devices
produced in Example 4 (Ex. 4 devices) and Comparative Example 4 (Comp. 4
devices), formed on the belt-like member, were cut out at intervals of 10
m in a size 5 cm square, and placed under irradiation by light of AM-1.5
(100 mW/cm.sup.2) to measure their photoelectric conversion efficiency.
Any scattering of the measurement results of the photoelectric conversion
efficiency was examined. Regarding the results on the photovoltaic devices
of Comparative Example 4 (Comp. 4 devices) as a standard, reciprocals of
the degree of scattering were calculated to obtain the results as shown in
Table 8.
To evaluate the defect density, 100 pieces of the photovoltaic devices
produced in Example 4 (Ex. 4 devices) and Comparative Example 4 (Comp. 4
devices), formed on the belt-like member, were cut out in a size 5 cm
square within the length 5 m at the middle portion thereof, and electric
currents in the reverse direction were measured to detect the presence or
absence of defects (imperfections) in the respective photovoltaic devices.
Regarding the results on the photovoltaic devices of Comparative Example 4
(Comp. 4 devices) as a standard, reciprocals of the number of defects were
calculated to obtain the results as shown in Table 8.
In Table 8, the uniformity of characteristics and defect density are
indicated as relative values with respect to those of Comparative Example
4 regarded as a standard.
As is seen from Table 8, the photovoltaic devices of Example 4 (Ex. 4
devices) show good results with respect to both the uniformity of
characteristics and the defect density, compared with the photovoltaic
devices of Comparative Example 4 (Comp. 4 devices), proving that the
present invention is effective.
In the following Examples, instances where sliding members as the sliding
mechanism are provided to vacuum chambers will be described.
EXAMPLE 5
In the apparatus as shown in FIG. 1, in place of the expansion-contraction
absorbing members 107, the sliding members as shown in FIG. 4 were
attached to four corners at the bottoms of the vacuum chambers 101, 102,
104 and 105, and photovoltaic devices were produced in the state these
vacuum chambers are readily shiftable on the stand.
The photovoltaic devices were produced under conditions as shown together
in Table 9.
In Table 9, the first-conductivity type layer was an n-type layer, and the
second-conductivity type layer was a p-type layer.
The extent of shift of each vacuum chamber, affected by thermal expansion
due to the plasma discharge and heating with lamp heaters in the vacuum
chambers was measured in the same manner as in Example 1. Here, the extent
of shift occurring when the vacuum chambers were heated was measured
regarding as the starting point the position of each vacuum chamber
standing at room temperature. Also, since the temperature of each vacuum
chamber reached a maximum point immediately before the plasma discharge
was stopped and the extent of shift of each vacuum chamber reached maximum
at that point of time, the maximum extent of shift of each vacuum chamber
was defined to be the extent of shift at this point of time. As a result
of this measurement, the extent of shift was 5 mm in respect of the vacuum
chambers 102 and 104 and 10 mm in respect of the vacuum chambers 101 and
105, which respectively shifted in the direction they went away from the
vacuum chamber 103 provided at the middle.
When the vacuum chambers were cooled to room temperature, the extent of
shift of these chambers became zero, and the respective vacuum chambers
returned to their original positions.
COMPARATIVE EXAMPLE 5
The sliding members as used in Example 5 were all detached and the vacuum
chambers were all fixed to the stand, where photovoltaic devices (Comp. 5
devices) were produced under entirely the same film-forming conditions as
in Example 5.
The extent of shift of each vacuum chamber, affected by thermal expansion
due to the plasma discharge in each vacuum chamber and the heating with
lamp heaters was measured in the same manner as in Example 5.
It was just like Example 5 that the temperature of each vacuum chamber
reached a maximum point immediately before the plasma discharge was
stopped. However, while in Example 5 the extent of shift of each vacuum
chamber reached a maximum (5 mm or 10 mm) at this point in time, the
extent of shift of each vacuum chamber in this Comparative Example 5 was,
as a result of measurement, 0.5 mm in respect of the vacuum chambers 102
and 104 and 1 mm in respect of the vacuum chambers 101 and 105, which
respectively shifted in the direction they went away from the vacuum
chamber 103 provided at the middle.
When the vacuum chambers were cooled to room temperature, the extent of
shift of these chambers became zero, and the respective vacuum chambers
returned to their original positions.
EVALUATION ON EXAMPLE 5 AND COMPARATIVE EXAMPLE 5
The uniformity of characteristics and density of defects in the
photovoltaic devices produced in Example 5 (Ex. 5 devices) and Comparative
Example 5 (Comp. 5 devices) were evaluated.
To evaluate the uniformity of characteristics, the photovoltaic devices
produced in Example 5 (Ex. 5 devices) and Comparative Example 5 (Comp. 5
devices), formed on the belt-like member, were cut out at intervals of 10
m in a size 5 cm square, and placed under irradiation by light of AM-1.5
(100 mW/cm.sup.2) to measure their photoelectric conversion efficiency.
Any scattering of the measurement results of the photoelectric conversion,
efficiency was examined. Regarding the results on the photovoltaic devices
of Comparative Example 5 (Comp. 5 devices) as a standard, reciprocals of
the degree of scattering were calculated to obtain the results as; shown
in Table 10.
To evaluate the defect density, 100 pieces of the photovoltaic devices
produced in Example 5 (Ex. 5 devices) and Comparative Example 5 (Comp. 5
devices), formed on the belt-like member, were cut out in a size of 5 cm
square within the length of 5 m at the middle portion thereof, and
electric currents in the reverse direction were measured to detect the
presence or absence of defects (imperfections) in the respective
photovoltaic devices. Regarding the results on the photovoltaic devices of
Comparative Example 5 (Comp. 5 devices) as a standard, reciprocals of the
number of defects were calculated to obtain the results as shown in Table
10.
It can be said that the higher the numerical values are, the better the
solar cells (photovoltaic devices) are on the whole with respect to both
the defect density and the uniformity of characteristics.
In Table 10, the uniformity of characteristics and defect density are
indicated as relative values with respect to those of Comparative Example
5 regarded as a standard.
As is seen from Table 10, the photovoltaic devices of Example 5 (Ex. 5
devices) show good results in respect of both the uniformity of
characteristics and the defect density, compared with the photovoltaic
devices of Comparative Example 5 (Comp. 5 devices), proving that the
present invention is effective.
EXAMPLE 6
Tandem type solar cells (photovoltaic devices) as shown in Table 9 were
produced, having two sets of pin junctions comprised of a
first-conductivity type layer, an i-type layer, a second-conductivity type
layer, a first-conductivity type layer, an i-type layer and a
second-conductivity type layer which were superposed on the lower
electrode.
The i-type layers were respectively formed of amorphous silicon germanium
in the first pin junction, and amorphous silicon in the second pin
junction.
The photovoltaic devices were produced under conditions as shown together
in Table 11.
In Table 11, the first-conductivity type layer was an n-type layer, and the
second-conductivity type layer was a p-type layer. Layers were superposed
in the order of the upper to lower columns as shown in the table.
In the present Example, eight vacuum chambers were provided in total.
In the case of this Example, the vacuum chambers were fixed in the
following way: The middle vacuum chamber for forming the p-type layer was
fixed to the stand only at one side of the bottom corners of the chamber,
and the sliding members as shown in FIG. 6 were attached to the other
bottom two corners of the middle vacuum chamber and also to the bottom
four corners of the remaining vacuum chambers.
Using the apparatus set up in this way, the tandem type solar cells were
produced according to the same process for producing photovoltaic devices
as in Example 5.
The extent of shift of each vacuum chamber, affected by thermal expansion
due to the plasma discharge and heating with lamp heaters in the vacuum
chambers was measured in the same manner as in Example 5. Here, the extent
of shift occurring when the vacuum chambers were heated was; measured
regarding as the starting point the position of each vacuum chamber
standing at room temperature. Also, since the temperature of each vacuum
chamber reached a maximum point immediately before the plasma discharge
was stopped and the extent of shift of each vacuum chamber became maximum
at that point in time, the maximum extent of shift of each vacuum chamber
was defined to be the extent of shift at this point in time.
As a result of this measurement, the extent of shift of the eight vacuum
chambers was 20 mm, 15 mm, 10 mm, 5 mm, 5 mm, 10 mm, 15 mm and 20 mm,
respectively, in the order starting from the substrate feed chamber, which
respectively shifted in the direction they went away from the fixed
position.
When the vacuum chambers were cooled to room temperature after a series of
production steps were completed, the extent of shift of these chambers
became zero, and these vacuum chambers returned to their original
positions.
COMPARATIVE EXAMPLE 6
The sliding members as used in Example 6 were all detached and the vacuum
chambers were all fixed to the stand, where photovoltaic devices (Comp. 6
devices) were produced under entirely the same film-forming conditions as
in Example 6.
The extent of shift of each vacuum chamber, affected by thermal expansion
due to the plasma discharge in each vacuum chamber and the heating with
lamp heaters was measured in the same manner as in Example 6.
It was just like Example 6 that the temperature of each vacuum chamber
reached a maximum point immediately before the plasma discharge was
stopped. However, while in Example 6 the extent of shift of each vacuum
chamber became maximum at this point of time, the extent of shift of each
vacuum chamber in this Comparative Example 6 was, as a result of
measurement, about 0.5 mm in respect of all the vacuum chambers.
When the vacuum chambers were well cooled to room temperature, the extent
of shift of these chambers became zero, and the respective vacuum chambers
were seen to have returned to original positions.
EVALUATION ON EXAMPLE 6 AND COMPARATIVE EXAMPLE 6
The uniformity of characteristics and density of defects in the
photovoltaic devices produced in Example 6 (Ex. 6 devices) and Comparative
Example 6 (Comp. 6 devices) were evaluated.
To evaluate the uniformity of characteristics, the photovoltaic devices
produced in Example 6 (Ex. 6 devices) and Comparative Example 6 (Comp. 6
devices), formed on the belt-like member, were cut out at intervals 10 m
in a size of 5 cm square, and placed under irradiation by light of AM-1.5
(100 mW/cm.sup.2) to measure their photoelectric conversion efficiency.
Any scattering of the measurement results of the photoelectric conversion
efficiency was examined. Regarding the results on the photovoltaic devices
of Comparative Example 6 (Comp. 6 devices) as a standard, reciprocals of
the degree of scattering were calculated to obtain the results as shown in
Table 12.
To evaluate the defect density, 100 pieces of the photovoltaic devices
produced in Example 6 (Ex. 6 devices) and Comparative Example 6 (Comp. 6
devices), formed on the belt-like member, were cut out in a size 5 cm
square within the length 5 m at the middle portion thereof, and electric
currents in the reverse direction were measured to detect the presence or
absence of defects (imperfections) in the respective photovoltaic devices.
Regarding the results on the photovoltaic devices of Comparative Example 6
(Comp. 6 devices) as a standard, reciprocals of the number of defects were
calculated to obtain the results as shown in Table 12.
In Table 12, the uniformity of characteristics and defect density are
indicated as relative values with respect to those of Comparative Example
6 regarded as a standard.
As is seen from Table 12, the photovoltaic devices of Example 6 (Ex. 6
devices) show good results with respect of both the uniformity to
characteristics and the defect density, compared with the photovoltaic
devices of Comparative Example 6 (Comp. 6 devices), proving that the
present invention is effective.
EXAMPLE 7
Triple type photovoltaic devices as shown in FIG. 9C were produced, having
three sets of pin junctions of first-conductivity type layers, i-type
layers and second-conductivity type layers which were superposed on the
lower electrode.
The i-type layers were respectively formed of amorphous silicon germanium
in the first pin junction, amorphous silicon germanium in the second pin
junction, and amorphous silicon in the third pin junction.
The photovoltaic devices were produced under conditions as shown together
in Table 13.
In Table 13, the first-conductivity type layer was an n-type layer, and the
second-conductivity type layer was a p-type layer. Layers were superposed
in the order of the upper to lower columns as shown in the table.
In the present Example, eleven vacuum chambers in total were provided.
In the case of this Example, the middle-positioned vacuum chamber was the
i-type layer forming vacuum chamber at the middle. The sliding members as
shown in FIG. 6 were attached to the bottom four corners of each vacuum
chamber.
Using the apparatus set up in this way, the triple type solar cells were
produced according to the same process for producing photovoltaic devices
as in Example 6.
The extent of shift of each vacuum chamber, affected by thermal expansion
due to the plasma discharge and heating with lamp heaters in the vacuum
chambers was measured in the same manner as in Example 6. Here, the extent
of shift occurring when the vacuum chambers were heated was measured
regarding as the starting point the position of each vacuum chamber
standing at room temperature. Also, since the temperature of each vacuum
chamber reached a maximum point immediately before the plasma discharge
was stopped and the extent of shift of each vacuum chamber reached a
maximum at that point of time, the maximum extent of shift of each vacuum
chamber was defined to be the extent of shift at this point of time.
As a result of this measurement, it was seen that, among the eleven vacuum
chambers, the middle i-type layer forming vacuum chamber did not shift and
the remaining vacuum chambers respectively shifted by 25 mm, 20 mm, 15 mm,
10 mm and 5 mm in the order of vacuum chambers distant from the middle
vacuum chamber.
When the vacuum chambers were cooled to room temperature after a series of
production steps were completed, the extent of shift of these chambers
became zero, and these vacuum chambers returned to their original
positions.
COMPARATIVE EXAMPLE 7
The sliding members as used in Example 7 were all detached and the vacuum
chambers were all fixed to the stand, where photovoltaic devices (Comp. 7
devices) were produced under entirely the same film-forming conditions as
in Example 7.
The extent of shift of each vacuum chamber, affected by thermal expansion
due to the plasma discharge in each vacuum chamber and the heating with
lamp heaters was measured in the same manner as in Example 7.
It was just like Example 7 that the temperature of each vacuum chamber
reached a maximum point immediately before the plasma discharge was
stopped. However, while in Example 7 the extent of shift of each vacuum
chamber became maximum at this point of time, the extent of shift of each
vacuum chamber in this Comparative Example 7 was, as a result of
measurement, about 0.5 mm, or about 0.6 mm even at maximum, in respect of
all the vacuum chambers.
When the vacuum chambers were cooled to room temperature, the extent of
shift of these chambers became zero, and the respective vacuum chambers
returned to their original positions.
EVALUATION ON EXAMPLE 7 AND COMPARATIVE EXAMPLE 7
The uniformity of characteristics and density of defects in the
photovoltaic devices produced in Example 7 (Ex. 7 devices) and Comparative
Example 7 (Comp. 7 devices) were evaluated.
To evaluate the uniformity of characteristics, the photovoltaic devices
produced in Example 7 (Ex. 7 devices) and Comparative Example 7 (Comp. 7
devices), formed on the belt-like member, were cut out at intervals of 10
m in a size 5 cm square, and placed under irradiation by light of AM-1.5
(100 mW/cm.sup.2) to measure their photoelectric conversion efficiency.
Any scattering of the measurement results of the photoelectric conversion
efficiency was examined. Regarding the results on the photovoltaic devices
of Comparative Example 7 (Comp. 7 devices) as a standard, reciprocals of
the degree of scattering were calculated to obtain the results as shown in
Table 14.
To evaluate the defect density, 100 pieces of the photovoltaic devices
produced in Example 7 (Ex. 7 devices) and Comparative Example 7 (Comp. 7
devices), formed on the belt-like member, were cut out in a size 5 cm
square within the length 5 m at the middle portion thereof, and electric
currents in the reverse direction were measured to detect the presence or
absence of defects (imperfections) in the respective photovoltaic devices.
Regarding the results on the photovoltaic devices of Comparative Example 7
(Comp. 7 devices) as a standard, reciprocals of the number of defects were
calculated to obtain the results as shown in Table 14.
In Table 14, the uniformity of characteristics and defect density are
indicated as relative values with respect to those of Comparative Example
7 regarded as a standard.
As is seen from Table 14, the photovoltaic devices of Example 7 (Ex. 7
devices) show good results with respect to both the uniformity of
characteristics and the defect density, compared with the photovoltaic
devices of Comparative Example 7 (Comp. 7 devices), proving that the
present invention is effective.
EXAMPLE 8
In the apparatus as shown in FIG. 1, vacuum chambers provided with the
sliding mechanism as shown in FIG. 7 were used in place of those provided
with the expansion-contraction absorbing members 107, and also the method
as used in Example 4 was used in which the belt-like member was bent in a
cylindrical form to make up film-forming space.
The photovoltaic devices were produced under conditions as shown together
in Table 15.
In Table 15, the first-conductivity type layer was an n-type layer, and the
second-conductivity type layer was a p-type layer. Layers were superposed
in the order of the upper to lower columns as shown in the table.
The extent of shift of each vacuum chamber, affected by thermal expansion
due to the plasma discharge and heating with lamp heaters in the vacuum
chambers was measured in the same manner as in Example 1. Here, the extent
of shift occurring when the vacuum chambers were heated was measured
regarding as the starting point the position of each vacuum chamber
standing at room temperature. Also, since the temperature of each vacuum
chamber reached a maximum point immediately before the plasma discharge
was stopped and the extent of shift of each vacuum chamber reached maximum
at that point of time, the maximum extent of shift of each vacuum chamber
was defined to be the extent of shift at this point of time. As a result
of this measurement, the extent of shift was 5 mm in respect of the vacuum
chambers 102 and 104 and 10 mm in respect of the vacuum chambers 101 and
105, which respectively shifted in the direction they went away from the
vacuum chamber 103 provided at the middle.
When the vacuum chambers were cooled to room temperature, the extent of
shift of these chambers became zero, and the respective vacuum chambers
returned to their original positions.
COMPARATIVE EXAMPLE 8
The sliding members and slide limiting members as used in Example 8 were
all detached and the vacuum chambers were all fixed to the stand, where
photovoltaic devices (Comp. 8 devices) were produced under entirely the
same film-forming conditions as in Example 8.
The extent of shift of each vacuum chamber, affected by thermal expansion
due to the plasma discharge in each vacuum chamber and the heating with
lamp heaters was measured in the same manner as in Example 8.
It was just like Example 8 that the temperature of each vacuum chamber
reached a maximum point immediately before the plasma discharge was
stopped. However, while in Example 8 the extent of shift of each vacuum
chamber became maximum at this point of time, the extent of shift of each
vacuum chamber in this Comparative Example 8 was, as a result of
measurement, 0.5 mm in respect of the vacuum chambers 102 and 104 and 1 mm
in respect of the vacuum chambers 101 and 105, which respectively shifted
in the direction they went away from the vacuum chamber 103 provided at
the middle.
When the vacuum chambers were cooled to room temperature, the extent of
shift of these chambers became zero, and the respective vacuum chambers
returned to their original positions.
EVALUATION ON EXAMPLE 8 AND COMPARATIVE EXAMPLE 8
The uniformity of characteristics and density of defects in the
photovoltaic devices produced in Example 8 (Ex. 8 devices) and Comparative
Example 8 (Comp. 8 devices) were evaluated.
To evaluate the uniformity of characteristics, the photovoltaic devices
produced in Example 8 (Ex. 8 devices) and Comparative Example 8 (Comp. 8
devices), formed on the belt-like member, were cut out at intervals of 10
m in a size 5 cm square, and placed under irradiation by light of AM-1.5
(100 mW/cm.sup.2) to measure their photoelectric conversion efficiency.
Any scattering of the measurement results of the photoelectric conversion
efficiency was examined. Regarding the results on the photovoltaic devices
of Comparative Example 8 (Comp. 8 devices) as a standard, reciprocals of
the degree of scattering were calculated to obtain the results as shown in
Table 16.
To evaluate the defect density, 100 pieces of the photovoltaic devices
produced in Example 8 (Ex. 8 devices) and Comparative Example 8 (Comp. 8
devices), formed on the belt-like member, were cut out in a size 5 cm
square within the length 5 m at the middle portion thereof, and electric
currents in the reverse direction were measured to detect the presence or
absence of defects (imperfections) in the respective photovoltaic devices.
Regarding the results on the photovoltaic devices of Comparative Example 8
(Comp. 8 devices) as a standard, reciprocals of the number of defects were
calculated to obtain the results as shown in Table 16.
In Table 16, the uniformity of characteristics and defect density are
indicated as relative values with respect to those of Comparative Example
8 regarded as a standard.
As is seen from Table 16, the photovoltaic devices of Example 8 (Ex. 8
devices) show good results with respect of both the uniformity to
characteristics and the defect density, compared with the photovoltaic
devices of Comparative Example 8 (Comp. 8 devices), proving that the
present invention is effective.
TABLE 1
______________________________________
Substrate:
SUS430BA; width: 120 mm; thickness: 0.13 mm
Reflecting layer:
Silver (Ag), 100 nm thin film
Reflection enhancing layer:
Zinc oxide (ZnO), 1 .mu.m thin film
Gate gas:
H.sub.2 from each gate, 700 sccm
Layer-forming conditions:
Gases used; Microwave Substrate
flow rate power Pressure temp.
(sccm) (W) (mTorr) (.degree. C.)
______________________________________
Layers
n-Type layer:
SiH.sub.4 20
PH.sub.3 /H.sub.2 100
1,000 30 300
(1% diluted)
H.sub.2 200
i-Type layer:
SiH.sub.4 200
H.sub.2 100 300 6 300
p-Type layer:
SiH.sub.4 10
BF.sub.3 /H.sub.2 50
1,000 30 300
(1% diluted)
H.sub.2 250
______________________________________
Transparent electrode: ITO(In.sub.2 O.sub.3 + SnO.sub.2), 70 nm thin fil
Collector electrode: aluminum (Al), 2 .mu.m thin film
TABLE 2
______________________________________
Uniformity of
Device No. characteristics
Defect density
______________________________________
Ex. 1 1.11 1.32
Comp. 1 1.00 1.00
______________________________________
TABLE 3
______________________________________
Layer-forming conditions:
Gases used; Microwave Substrate
flow rate power pressure temp.
(sccm) (W) (mTorr) (.degree. C.)
______________________________________
Layers
n-Type layer:
SiH.sub.4 20
PH.sub.3 /H.sub.2 100
1,000 30 350
(1% diluted)
H.sub.2 200
i-Type layer:
SiH.sub.4 200
GeH.sub.4 50
250 7 350
H.sub.2 100
p-Type layer:
SiH.sub.4 10
BF.sub.3 /H.sub.2 50
1,000 30 350
(1% diluted)
H.sub.2 250
n-Type layer:
SiH.sub.4 20
PH.sub.3 /H.sub.2 100
1,000 30 300
(1% diluted)
H.sub.2 200
i-Type layer:
SiH.sub.4 200
H.sub.2 100 250 6 300
p-Type layer:
SiH.sub.4 10
BF.sub.3 /H.sub.2 50
1,000 30 300
(1% diluted)
H.sub.2 250
______________________________________
TABLE 4
______________________________________
Uniformity of
Device No. characteristics
Defect density
______________________________________
Ex. 2 1.10 1.45
Comp. 2 1.00 1.00
______________________________________
TABLE 5
______________________________________
Layer-forming conditions:
Gases used; Microwave Substrate
flow rate power Pressure temp.
(sccm) (W) (mTorr) (.degree. C.)
______________________________________
Layers
n-Type layer:
SiH.sub.4 20
PH.sub.3 /H.sub.2 100
1,000 30 350
(1% diluted)
H.sub.2 200
i-Type layer:
SiH.sub.4 200
GeH.sub.4 50
200 7 350
H.sub.2 100
p-Type layer:
SiH.sub.4 10
BF.sub.3 /H.sub.2 50
1,000 30 350
(1% diluted)
H.sub.2 250
n-Type layer:
SiH.sub.4 20
PH.sub.3 /H.sub.2 100
1,000 30 300
(1% diluted)
H.sub.2 200
i-Type layer:
SiH.sub.4 200
H.sub.2 100 250 6 300
p-Type layer:
SiH.sub.4 10
BF.sub.3 /H.sub.2 50
1,000 30 300
(1% diluted)
H.sub.2 250
n-Type layer:
SiH.sub.4 20
PH.sub.3 /H.sub.2 100
1,000 30 250
(1% diluted)
H.sub.2 200
i-Type layer:
SiH.sub.4 200
H.sub.2 100 200 5 250
p-Type layer:
SiH.sub.4 10
BF.sub.3 /H.sub.2 50
1,000 30 250
(1% diluted)
H.sub.2 250
______________________________________
TABLE 6
______________________________________
Uniformity of
Device No. characteristics
Defect density
______________________________________
Ex. 3 1.12 1.44
Comp. 3 1.00 1.00
______________________________________
TABLE 7
______________________________________
Substrate:
SUS430BA; width: 360 mm; thickness: 0.13 mm
Reflecting layer:
Silver (Ag), 100 nm thin film
Reflection enhancing layer:
Zinc oxide (ZnO), 1 .mu.m thin film
Gate gas:
H.sub.2 from each gate, 700 sccm
Layer-forming conditions:
Gases used; Microwave Substrate
flow rate power Pressure temp.
(sccm) (W) (mTorr) (.degree. C.)
______________________________________
Layers
n-Type layer:
SiH.sub.4 40
PH.sub.3 /H.sub.2 200
800/800 40 350
(1% diluted)
H.sub.2 400
i-Type layer:
SiH.sub.4 400
H.sub.2 200 500/500 5 350
p-Type layer:
SiH.sub.4 20
BF.sub.3 /H.sub.2 100
800/800 40 350
(1% diluted)
H.sub.2 500
______________________________________
Transparent electrode: ITO(In.sub.2 O.sub.3 + SnO.sub.2), 70 nm thin fil
Collector electrode: aluminum (Al), 2 .mu.m thin film
TABLE 8
______________________________________
Uniformity of
Device No. characteristics
Defect density
______________________________________
Ex. 4 1.13 1.25
Comp. 4 1.00 1.00
______________________________________
TABLE 9
______________________________________
Substrate:
SUS430BA; width: 120 mm; thickness: 0.13 mm
Reflecting layer:
Silver (Ag), 100 nm thin film
Reflection enhancing layer:
Zinc oxide (ZnO), 1 .mu.m thin film
Gate gas:
H.sub.2 from each gate, 700 sccm
Layer-forming conditions:
Gases used;
Microwave Substrate
flow rate power Pressure
temp.
Layers (sccm) (W) (mTorr)
(.degree. C.)
______________________________________
n-Type layer:
SiH.sub.4 20
PH.sub.3 /H.sub.2
100 1,000 30 300
(1% diluted)
H.sub.2 200
i-Type layer:
SiH.sub.4 200
H.sub.2 100 300 6 300
p-Type layer:
SiH.sub.4 10
BF.sub.3 /H.sub.2
50 1,000 30 300
(1% diluted)
H.sub.2 250
Transparent electrode: ITO (In.sub.2 O.sub.3 + SnO.sub.2), 70 nm thin
film
Collector electrode: aluminum (Al), 2 .mu.m thin film
______________________________________
TABLE 10
______________________________________
Uniformity of
Device No. characteristics
Defect density
______________________________________
Ex. 5 1.15 1.35
Comp. 5 1.00 1.00
______________________________________
TABLE 11
______________________________________
Layer-forming conditions:
Gases used;
Microwave Substrate
flow rate power Pressure
temp.
Layers (sccm) (W) (mTorr)
(.degree. C.)
______________________________________
n-Type layer:
SiH.sub.4 20
PH.sub.3 /H.sub.2
100 1,000 30 350
(1% diluted)
H.sub.2 200
i-Type layer:
SiH.sub.4 200
GeH.sub.4 50 250 7 350
H.sub.2 100
p-Type layer:
SiH.sub.4 10
BF.sub.3 /H.sub.2
50 1,000 30 350
(1% diluted)
H.sub.2 250
n-Type layer:
SiH.sub.4 20
PH.sub.3 /H.sub.2
100 1,000 30 300
(1% diluted)
H.sub.2 200
i-Type layer:
SiH.sub.4 200
H.sub.2 100 250 6 300
p-Type layer:
SiH.sub.4 10
BF.sub.3 /H.sub.2
50 1,000 30 300
(1% diluted)
H.sub.2 250
______________________________________
TABLE 12
______________________________________
Uniformity of
Device No. characteristics
Defect density
______________________________________
Ex. 6 1.18 1.41
Comp. 6 1.00 1.00
______________________________________
TABLE 13
______________________________________
Layer-forming conditions:
Gases used;
Microwave Substrate
flow rate power Pressure
temp.
Layers (sccm) (W) (mTorr)
(.degree. C.)
______________________________________
n-Type layer:
SiH.sub.4 20
PH.sub.3 /H.sub.2
100 1,000 30 350
(1% diluted)
H.sub.2 200
i-Type layer:
SiH.sub.4 200
GeH.sub.4 50 200 7 350
H.sub.2 100
p-Type layer:
SiH.sub.4 10
BF.sub.3 /H.sub.2
50 1,000 30 350
(1% diluted)
H.sub.2 250
n-Type layer:
SiH.sub.4 20
PH.sub.3 /H.sub.2
100 1,000 30 300
(1% diluted)
H.sub.2 200
i-Type layer:
SiH.sub.4 200
H.sub.2 100 250 6 300
p-Type layer:
SiH.sub.4 10
BF.sub.3 /H.sub.2
50 1,000 30 300
(1% diluted)
H.sub.2 250
n-Type layer:
SiH.sub.4 20
PH.sub.3 /H.sub.2
100 1,000 30 250
(1% diluted)
H.sub.2 200
i-Type layer:
SiH.sub.4 200
H.sub.2 100 200 5 250
p-Type layer:
SiH.sub.4 10
BF.sub.3 /H.sub.2
50 1,000 30 250
(1% diluted)
H.sub.2 250
______________________________________
TABLE 14
______________________________________
Uniformity of
Device No. characteristics
Defect density
______________________________________
Ex. 7 1.15 1.40
Comp. 7 1.00 1.00
______________________________________
TABLE 15
______________________________________
Substrate:
SUS430BA; width: 360 mm; thickness: 0.13 mm
Reflecting layer:
Silver (Ag), 100 nm thin film
Reflection enhancing layer:
Zinc oxide (ZnO), 1 .mu.m thin film
Gate gas:
H.sub.2 from each gate, 700 sccm
Layer-forming conditions:
Gases used;
Microwave Substrate
flow rate power Pressure
temp.
Layers (sccm) (W) (mTorr)
(.degree. C.)
______________________________________
n-Type layer:
SiH.sub.4 40
PH.sub.3 /H.sub.2
200 800/800 40 350
(1% diluted)
H.sub.2 400
i-Type layer:
SiH.sub.4 400
H.sub.2 200 500/500 5 350
p-Type layer:
SiH.sub.4 20
BF.sub.3 /H.sub.2
100 800/800 40 350
(1% diluted)
H.sub.2 500
Transparent electrode: ITO (In.sub.2 O.sub.3 + SnO.sub.2), 70 nm thin
film
Collector electrode: aluminum (Al), 2 .mu.m thin film
______________________________________
TABLE 16
______________________________________
Uniformity of
Device No. characteristics
Defect density
______________________________________
Ex. 8 1.11 1.22
Comp. 8 1.00 1.00
______________________________________
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